Tuesday, January 22, 2008

To make proteins with amino acids that aren’t specified in the genetic code

Chemists solve biological challenge

Chemistry professor Ronald Kluger and PhD candidate Svetlana Tzvetkova have made discoveries that could not only allow scientists to generate new kinds of proteins —the building blocks of life—but also eventually lead to practical applications such as simplifying drug development and manufacturing.

These chemists have stretched the bounds of nature and genetics by chemically, rather than biologically,modifying the steps involved in creating proteins. Kluger became interested in the possibility of manipulating proteins after learning about efforts to produce “designer amino acids.”

“I was intrigued by the possibility that someone could actually attempt to makeproteins with amino acids that aren’t specified in the genetic code at all,” Kluger explained.

Nature defines 20 different amino acids that can link together to make proteins. But protein creation begins with deoxyribonucleic acid (DNA), which sends out genetic instructions via an RNA message (mRNA) to the ribosomes in our cells. Transfer ribonucleic acids (tRNA) collect the amino acids and bring them to the ribosomes. The tRNA then aligns with mRNA so the amino acids can join to form proteins. The catch is that an amino acid has to be activated by a specific enzyme before the tRNA can scoop it up.

Kluger and former student Lisa Cameron found that they could mimic the critical action of this enzyme when they combined common inorganic chemicals called lanthanum salts with a chemically activated amino acid. It was Tzvetkova who showed that this chemical mimic will allow an amino acid to attach to the complex tRNA molecule in just the right place.